Bug 847168 - [User Story] Email Signature

You should use modifyIdentity instead of directly clobbering the state.  That will give us coverage of modifyIdentity which is honestly a lot of what we're looking for in this test.

That should happen in its own T.action step and you'll want to also verify that our requested update is reflected on the identity *after* we get the onchange notification from the BridgedViewSlice that contains it.  So you'll probably want an expectation on the modifyIdentity callback and also one on the "onchange" firing and the state being correct.

Note that it's okay to use helper functions to effectively parameterize all this.  Either by adding them in th_main or just in the function.

Like:
do_setSignature('test 1', true);
do_composeAndVerifyBody('\n\n--\ntest 1');

Also nit: "test 1" and its friends have double quotes instead of single quotes.